I did a google for the phrase and found that the question was from 2009, 13 years ago.
So - if you had searched for the question at the time, there wouldn't have been a duplicate. There are a few factors here. We've refined what's acceptable here based on experience - consider the old boat programming meme and our policies in general on recommendation questions. Our quality standards have also gotten significantly stricter since then. You can't always judge the responses of users today based off the past.
I guess it feels unfair, but that's a 'perk' of being an early user.
Simply - it was a question that had never been asked before then and added to the knowledge base. You can refer back to it. You can even ask a new question if slicing has changed over new versions of Python changed the slicing syntax referencing this question and its answers. I've occasionally personally repackaged a bit of knowledge that I picked up elsewhere as a post on various sites so it’s findable here.
As such, a good many people googled "How does slicing work in Python" as I did, found the answer, and if they had the same problem, upvoted the question for being there when they needed it and any useful answers. As we often tell people—you're not asking a question just for you; you're asking a question for the next person with the same problem, or in this case the next 4336.
It’s not about grammar or spelling; it’s about answerability (there being a solvable problem), interestingness and effort. Yes, that was a simple question from another time - we've grown (huge!) and things work differently now.